Nylon 6 is commonly spun into fibers that are combined to make yarns that find use in such areas as carpeting and upholstery. Nylon 6 has physical properties that make it excellent for these end uses.
In some applications, especially in carpet applications, nylon 6 yarn is subject to heat treatment referred to as "heatsetting". Heatsetting confers dimensional stability and improved heat resistance (among other things) on the yarns subjected to it. For twisted plied yarns, heatsetting relieves mechanical twisting stresses, thus conferring improved twist retention and appearance retention to carpet made from such twisted yarns. The heatsetting process is known to cause nylon 6 yarns to shrink. It would be desirable to have a yarn displaying the advantageous nylon 6 characteristics, but with less heatset shrinkage.
Compatibilized blends of polyamides and other polymers have been spun into fibers. U.S. Pat. No. 5,759,925 to Ballard et al. describes fibers spun from blends of polyphenylene sulfide and polyamide compatibilized with modified polyolefins.
Polymer alloys of nylon 6, polyolefin and a compatibilizer have been studied extensively. Representative examples of such studies are presented in S. S. Dagli, M. Xanthos and J. A. Biesenberger, Effects of Extrusion Parameters on the Morphology and Properties of Compatibilized Nylon 6/Polypropylene Blends, Compalloy '91, pp. 257-276; F. Ide and A. Hasegawa, Studies on Polymer Blend of Nylon 6 and Polypropylene or Nylon 6 and Polystyrene Using the Reaction of Polymer, J. Appl. Polym. Sci., Vol. 18, pp. 963-974 (1974); S. J. Park, B. Y. Kim and H. M. Jeong, Morphological, Thermal and Rheological Properties of the Blends Polypropylene/Nylon-6, Polypropylene/Nylon-6 (Maleic Anhydride-g-Polypropylene) and (Maleic Anhydride-g-Polypropylene)/Nylon-6, Eur. Polym. J., Vol. 26, No. 2, pp. 131-136 (1990); F. P. Mantia, Blends of Polypropylene and Nylon 6: Influence of the Compatibilizer, Molecular Weight, and Processing Conditions, Advances in Polymer Technology, Vol. 12, No. 1, pp. 47-59 (1993); A. R. Padwa, Compatibilized Blends of Polyamide-6 and Polyethylene, Polymer Engineering and Science, Vol. 32, No. 22, pp. 1703-1710 (1992); U.S. Pat. No. 5,683,818 to Bolvari; and U.S. Pat. No. 5,719,198 to Young et al.
Blends of nylon and polyolefin have been extruded into fibers. U.S. Pat. No. 3,793,822 to Kawai describes a fishing net formed of monofilaments 200-2000 denier thick which are preferably made from polyamide blended with polypropylene.
Compatibilized alloys of nylon 6 and polypropylene have been spun into fibers. U.S. Pat. No. 4,822,678 to Brody et al. describes fibers spun from blends of polyamides and polyolefins that are compatibilized with a nylon 11. EPA 0 658 640 describes monofilaments spun from polyamide and polypropylene compatibilized with bonding agents, including maleated polypropylene.